RFR: 8256172: Clean up CDS handling of i2i_entry [v2]

[Yumin Qi]

On Wed, 18 Nov 2020 18:12:15 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> This PR is a prerequisite for [JDK-8250989](https://bugs.openjdk.java.net/browse/JDK-8250989) - Consolidate buffer allocation code for CDS static/dynamic archive dumping.
>> 
>> -  Move the allocation of the i2i buffer after all classes are loaded. This makes it possible to estimate the size of the CDS archive before we allocate the output space (this is what dynamic archive does now).
>> - No need to generate the i2i trampoline code during -Xshare:dump
>> - Clean up the CDS code in abstractInterpreter.cpp and add more comments.
>
> Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:
> 
>  - fixed merge
>  - Merge branch 'master' into 8256172-cleanup-cds-i2i-entry
>  - 8256172: Clean up CDS handling of i2i_entry

Look good to me.

src/hotspot/share/memory/metaspaceShared.cpp line 513:

> 511:   // We don't want any valid object to be at the very bottom of the archive.
> 512:   // See ArchivePtrMarker::mark_pointer().
> 513:   MetaspaceShared::misc_code_space_alloc(16);

16 looks arbitrary number though we know it is minimal object alignment --- maybe we we can use object_alignment instead? up to you.

-------------

Marked as reviewed by minqi (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1280